< draft-briscoe-docsis-q-protection-04.txt		draft-briscoe-docsis-q-protection-05.txt >
	Network Working Group B. Briscoe, Ed.		Network Working Group B. Briscoe, Ed.
	Internet-Draft Independent		Internet-Draft Independent
	Intended status: Informational G. White		Intended status: Informational G. White
	Expires: 11 November 2022 CableLabs		Expires: 12 November 2022 CableLabs
	10 May 2022		11 May 2022
	The DOCSIS® Queue Protection Algorithm to Preserve Low Latency		The DOCSIS® Queue Protection Algorithm to Preserve Low Latency
	draft-briscoe-docsis-q-protection-04		draft-briscoe-docsis-q-protection-05
	Abstract		Abstract
	This informational document explains the specification of the queue		This informational document explains the specification of the queue
	protection algorithm used in DOCSIS technology since version 3.1. A		protection algorithm used in DOCSIS technology since version 3.1. A
	shared low latency queue relies on the non-queue-building behaviour		shared low latency queue relies on the non-queue-building behaviour
	of every traffic flow using it. However, some flows might not take		of every traffic flow using it. However, some flows might not take
	such care, either accidentally or maliciously. If a queue is about		such care, either accidentally or maliciously. If a queue is about
	to exceed a threshold level of delay, the queue protection algorithm		to exceed a threshold level of delay, the queue protection algorithm
	can rapidly detect the flows most likely to be responsible. It can		can rapidly detect the flows most likely to be responsible. It can
	skipping to change at page 1, line 45 ¶		skipping to change at page 1, line 45 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on 11 November 2022.		This Internet-Draft will expire on 12 November 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2022 IETF Trust and the persons identified as the		Copyright (c) 2022 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 3, line 43 ¶		skipping to change at page 3, line 43 ¶
	from the harm due to excess queuing that would otherwise be caused by		from the harm due to excess queuing that would otherwise be caused by
	such anomalous behaviour.		such anomalous behaviour.
	In normal scenarios without misclassified traffic, QProt is not		In normal scenarios without misclassified traffic, QProt is not
	expected to intervene at all in the classification or forwarding of		expected to intervene at all in the classification or forwarding of
	packets.		packets.
	An overview of how low latency support has been added to DOCSIS		An overview of how low latency support has been added to DOCSIS
	technology is given in [LLD]. In each direction of a DOCSIS link		technology is given in [LLD]. In each direction of a DOCSIS link
	(upstream and downstream), there are two queues: one for Low Latency		(upstream and downstream), there are two queues: one for Low Latency
	and one for Classic traffic, in an arrangement similar to the IETF's		(LL) and one for Classic traffic, in an arrangement similar to the
	Coupled DualQ AQM [I-D.ietf-tsvwg-aqm-dualq-coupled]. The two queues		IETF's Coupled DualQ AQM [I-D.ietf-tsvwg-aqm-dualq-coupled]. The two
	enable a transition from 'Classic' to 'Scalable' congestion control		queues enable a transition from 'Classic' to 'Scalable' congestion
	so that low latency can become the norm for any application,		control so that low latency can become the norm for any application,
	including ones seeking both full throughput and low latency, not just		including ones seeking both full throughput and low latency, not just
	low-rate applications that have been more traditionally associated		low-rate applications that have been more traditionally associated
	with a low latency service. The Classic queue is only necessary for		with a low latency service. The Classic queue is only necessary for
	traffic such as traditional (Reno/Cubic) TCP that needs about a round		traffic such as traditional (Reno/Cubic) TCP that needs about a round
	trip of buffering to fully utilize the link, and therefore has no		trip of buffering to fully utilize the link, and therefore has no
	incentive to mismark itself as low latency. The QProt function is		incentive to mismark itself as low latency. The QProt function is
	located at the ingress to the Low Latency queue. Therefore, in the		located at the ingress to the Low Latency queue. Therefore, in the
	upstream QProt is located on the cable modem (CM), and in the		upstream QProt is located on the cable modem (CM), and in the
	downstream it is located on the cable CMTS (CM Termination System).		downstream it is located on the cable CMTS (CM Termination System).
	If an arriving packet triggers queue protection, the QProt algorithm		If an arriving packet triggers queue protection, the QProt algorithm
	skipping to change at page 11, line 39 ¶		skipping to change at page 11, line 39 ¶
	* either of:		* either of:
	- source and destination port numbers, for TCP, UDP, UDP-Lite,		- source and destination port numbers, for TCP, UDP, UDP-Lite,
	SCTP, DCCP, etc.		SCTP, DCCP, etc.
	- Security Parameters Index (SPI) for IPSec Encapsulating		- Security Parameters Index (SPI) for IPSec Encapsulating
	Security Payload (ESP) [RFC4303].		Security Payload (ESP) [RFC4303].
	The Microflow Classification section of the Queue Protection Annex of		The Microflow Classification section of the Queue Protection Annex of
	the DOCSIS spec. [DOCSIS] defines various strategies to find these		the DOCSIS spec. [DOCSIS] defines various strategies to find these
	headers by skipping extension headers or encapsulations. If they		headers by skipping extension headers or encapsulations. If they
	cannot be found, the spec. defines various less-specific 3-tuples		cannot be found, the spec. defines various less-specific 3-tuples
	that would be used. The DOCSIS spec. should be referred to for all		that would be used. The DOCSIS spec. should be referred to for all
	these strategies, which will not be repeated here.		these strategies, which will not be repeated here.
	The array of bucket structures defined below is used by all the Queue		The array of bucket structures defined below is used by all the Queue
	Protection functions:		Protection functions:
	<CODE BEGINS>		<CODE BEGINS>
	struct bucket { // The leaky bucket structure to hold per-flow state		struct bucket { // The leaky bucket structure to hold per-flow state
	skipping to change at page 29, line 16 ¶		skipping to change at page 29, line 16 ¶
	redirection of whole-flows once enough of the individual packets of a		redirection of whole-flows once enough of the individual packets of a
	certain offending flow had been redirected. This would free up the		certain offending flow had been redirected. This would free up the
	buckets used to maintain the per-packet queuing score of persistent		buckets used to maintain the per-packet queuing score of persistent
	offenders. Whole-flow redirection is outside the scope of the		offenders. Whole-flow redirection is outside the scope of the
	current version of the QProt algorithm specified here, but it is		current version of the QProt algorithm specified here, but it is
	briefly discussed at the end of Section 5.5.		briefly discussed at the end of Section 5.5.
	It might be considered that all the packets of persistently offending		It might be considered that all the packets of persistently offending
	flows ought to be discarded rather than redirected. However, this is		flows ought to be discarded rather than redirected. However, this is
	not recommended, because attack flows might be able to pervert whole-		not recommended, because attack flows might be able to pervert whole-
	flow discard, turning it onto at least some innocent flows. thus		flow discard, turning it onto at least some innocent flows, thus
	amplifying an attack that causes reordering into total deletion of		amplifying an attack that causes reordering into total deletion of
	some innocent flows.		some innocent flows.
	9.1.2. Exhausting Processing Resources		9.1.2. Exhausting Processing Resources
	The processing time needed to apply the QProt algorithm to each L		The processing time needed to apply the QProt algorithm to each L
	packet is small and intended not to take all the time available		packet is small and intended not to take all the time available
	between each of a run of fairly small packets. However, an attack		between each of a run of fairly small packets. However, an attack
	could use minimum size packets launched from multiple input		could use minimum size packets launched from multiple input
	interfaces into a lower capacity output interface. Whether the QProt		interfaces into a lower capacity output interface. Whether the QProt
End of changes. 6 change blocks.
	10 lines changed or deleted		10 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/